Research on Control Method of Linear-Generator System Used for Free-Piston Energy Converter in Range Extenders

Free-Piston Energy Converter (FPEC) eliminates the crank connecting rod mechanism to realize variable compression ratio. This characteristic gives FPEC multi-fuel adaptability to achieve clean fuel power generation and higher efficiency. However, the lack of crank connecting rod mechanism makes FPEC susceptible to interference, and it is difficult to achieve stable operation. This paper focuses on the control method of Linear-Generator System (LGS) and the design of LGS controller. The LGS controller is composed of force controller and current controller. In Matlab / Simulink, we established the mathematical models of FPEC, where the LGS controller successfully realized the stable operation of FPEC with the target compression ratio, under the conditions of combustion fluctuations and external interference. And the tolerance of actual compression ratio is within 1%. Therefore, the control method is effective, and we can assume that FPEC as a range extender for hybrid vehicles has promising future adoption.